Educated at
Sedbergh School and the
Royal Military College, Sandhurst, Cassels was
commissioned into the
Indian Staff Corps as a second lieutenant on 22 January 1896. He received promotion to lieutenant on 22 April 1898, to captain on 22 January 1905 and to major on 22 January 1914. Whilst serving in India, Cassels made a single appearance in
first-class cricket for the
Europeans cricket team against the
Parsees at
Bombay in the 1902–03
Bombay Presidency Match. Batting twice in the match, he was dismissed for 2 runs in the Europeans first innings by
Ardeshir Mehta, whilst in their second innings he was dismissed
without scoring by
Maneksha Bulsara. He went on to serve in the
First World War, receiving rapid and successive promotion to temporary lieutenant colonel on 19 January 1916, brevet lieutenant colonel on 3 June 1916, brevet colonel in June 1917, In November 1917 he was appointed
Commander of
11th Indian Cavalry Brigade and took his brigade on a great turning movement up the left bank of the
River Tigris, outflanking the
Turks and helping to bring the
Mesopotamian Campaign to an end. Following the war, he briefly commanded the
18th Indian Division while it was stationed in the
Middle East. Cassels was promoted to
major general on 1 January 1919 in the
Cavalry in India when he was appointed
Commander of
Peshawar District. He was promoted to general on 15 October 1929 and appointed
General Officer Commanding-in-Chief of
Northern Command, India in 1930. He was next made
Commander-in-Chief, India and a Member of the
Executive Council of the
Governor-General of India in 1935. He continued in that post into the
Second World War and retired in 1941. ==Honours==